What Could Cause Trouble Getting Erections For The Past Week?

Hello sir. Iam 26 years old male unmarried. I have been very good in sex . I had many girlfriends and i had sex nearly 30 times. I often masturbate also. Previously i could do that 5 to 6 times a day. And still i was able to do one more time. But for the past one week or ten days i am having problem of erection. Iam using follihair tablets for one month. I don t think that medicine caused this. But i want to know why all of sudden iam unable to erect my penise as before? I watch porn also. Pls answer my question